In a typical ink jet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water and an organic material such as a monohydric alcohol, a polyhydric alcohol or mixtures thereof.
An ink jet recording element typically comprises a support having on at least one surface thereof an ink-receiving or image-receiving layer, and includes those intended for reflection viewing, which have an opaque support, and those intended for viewing by transmitted light, which have a transparent support.
An important characteristic of ink jet recording elements is their need to dry quickly after printing. To this end, porous recording elements have been developed which provide nearly instantaneous drying as long as they have sufficient thickness and pore volume to effectively contain the liquid ink. For example, a porous recording element can be manufactured by cast coating, in which a particulate-containing coating is applied to a support and is dried in contact with a polished smooth surface.
One of the major disadvantages of the current ink jet recording element is “differential gloss”, particular on images printed using pigment-based inks. In pigment-based inks, the colorant exists as discrete particles. These pigment particles are usually treated with addenda known as dispersants or stabilizers which serve to keep the pigment particles from agglomerating and/or settling out. Therefore, when the pigment-based inks are printed on recording elements having glossy surfaces, the inks on the imaged areas tend to stay on the surface of the receiver. “Differential gloss” describes the image artifact where the gloss of the non-imaged areas is very different from that of imaged areas. This type of image quality defects can be quite noticeable, even to ordinary observers. Although not designed to improve “differential gloss”, one possible solution to this problem is to cover the entire receiver with a protective layer through techniques such as laminating the printed image, or fusing the top fusible polymeric layer, in receivers to a continuous overcoat layer, such as those disclosed in U.S. patent application Ser. No. 09/954,779, filed on Sep. 18, 2001 of Wexler, or coating a protective layer on the imaged areas as described in EP1057646 and EP1048466. However, all these approaches involve separate steps after printing, making the entire process complex and costly.
What the art needs is a way to minimize gloss level variations in imaged and non-imaged areas when the various inks are deposited and dried on a receiver. This should be done as part of the printing process and not as a separate step after printing.